Thermodynamic formulation of wall slip

We develop a description of wall slip within a systematic framework of nonequilibrium thermodynamics. Whereas the underlying ideas are completely general, the concrete formulation is given for a temporary network model of entangled polymer melts and fixed walls. A coupled set of time-evolution equations for carefully motivated bulk and boundary variables is obtained from thermodynamic building blocks, in particular, energy and entropy as the generators of reversible and irreversible dynamics. The boundary conditions for the bulk equations are obtained in terms of the evolving boundary variables. A Giesekus-type expression for the wall shear stress as a function of slip velocity and some simple estimates for the vastly different slopes of this function at low- and high-shear stresses are the main results of this paper.